Fatigue loads on wind turbines of different control strategies operating in complex terrain

摘要

The impact of complex terrain wind conditions on the loading of wind turbines is examined using state-of-art computational means. The analysis is two folded. The first part considers variations of all the wind defining parameters: the turbulence intensities of the wind inflow, the corresponding length scales, the coherence decay factors, the vertical and lateral mean shears, the yaw misalignment and the mean velocity at the hub height. Running several wind turbines it is found that the main driving fatigue mechanism is, as expected, the turbulence intensity. Small length scales and strong three-dimensionality of the inflow, which are characteristic of complex terrains, are secondary factors of increase of the fatigue loads but still in some cases significant. The significance of yaw misalignment is confirmed. In the second part of the work different design concepts are compared in terms of fatigue loads. Four designs at the class of 0.5 MW machines are considered: a classical stall and a classical pitch regulated machine, a "structurally soft" stall machine and a fixed pitch variable speed machine. As regards the significance of the control strategy, it is found that there are no merits for any of the. The "soft" design however seems to have reduced loads.